Microwave stethoscope for measuring cardio-pulmonary vital signs and lung water content

Patent metadata

Field	Value
Publication number	US-9526438-B2
Application number	US-201414261884-A
Country	US
Kind code	B2
Filing date	Apr 25, 2014
Priority date	Apr 26, 2013
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

A microwave stethoscope measurement method and sensor design employ a microwave transmission sensor and a microwave reception sensor placed on a patient's chest in spaced-apart side-by-side configuration for monitoring patient vital signs, lung water content and other critical measurements. The side-by-side sensors are spaced apart a separation distance of about 1-3 cm in lateral chest orientation. The sensors may be formed with a textile fabric for wearer comfort and to improve contact with the patient's skin. The microwave sensor measurements are digitally processed using a modified short time Fourier Transform (STFT) spectrum windowed-averaged algorithm. Output data extracted from the microwave sensor measurements may be transmitted wirelessly to a mobile device such as a smartphone for remote monitoring of the patient's medical condition.

First claim

The invention claimed is:

1. A microwave stethoscope measurement apparatus comprising: a microwave transmission sensor and a microwave reception sensor in spaced-apart side-by-side configuration adapted to be placed on a patient's chest to over a selected heart-lung location in the body of the patient for monitoring lung water content and other vital signs of the patient, wherein the sensors are mounted on a single chest patch to be placed on the patient's chest, a microwave-frequency transmission/reception module coupled to said microwave transmission sensor to provide a microwave radiating signal from the patient's chest to the selected heart lung location in the patient's body from said microwave transmission sensor on the chest patch, and coupled to said microwave reception sensor to receive a microwave scattering signal returned from tissues at the selected heart-lung location in the patient's body to said microwave reception sensor on the chest patch, said returned microwave scattering signal being provided to said microwave-frequency transmission/reception module to be digitally analyzed for monitoring of lung water content; wherein the side-by-side microwave transmission and reception sensors are spaced apart a separation distance of 1-3 cm between sensors in lateral chest orientation on the chest patch in order to minimize attenuation of the returned microwave signal and/or electromagnetic coupling between the sensors so as to provide an optimal returned microwave signal for analysis of lung water content and other vital signs of the patient.

2. A microwave stethoscope measurement apparatus according to claim 1 , wherein said microwave transmission sensor has a coplanar waveguide structure with a conductive ground plane and a center microline strip in a central aperture of the ground plane that is carried on a substrate.

3. A microwave stethoscope measurement apparatus according to claim 1 , wherein said microwave transmission sensor is fed a transmitted microwave signal from said microwave-frequency transmission/reception module having a frequency range from about 700 MHz to 1.5 GHz.

4. A microwave stethoscope measurement apparatus according to claim 3 , wherein the frequency range of the transmitted microwave signal fed from said microwave-frequency transmission/reception module is from about 915 MHz and 920 MHz allocated for medical and industrial applications (ISM band).

5. A microwave stethoscope measurement apparatus according to claim 1 , wherein said microwave transmission sensor is a broadband sensor for multi-frequency measurements.

6. A microwave stethoscope measurement apparatus according to claim 1 , wherein said microwave transmission sensor is fabricated as a textile sensor for wearer comfort and to improve contact with the patient's skin.

7. A microwave stethoscope measurement apparatus according to claim 6 , wherein said textile sensor is comprised of conductive steel thread embroidered with nylon thread on a felt fabric.

8. A microwave stethoscope measurement apparatus according to claim 7 , wherein the embroidered steel thread forms the conductive ground plane and center transmission line, and a coaxial cable is sewn in electrical contact with the back of the ground plane and the center transmission line through the felt.

9. A microwave stethoscope measurement apparatus according to claim 8 , wherein said textile sensor is sewn to a cloth patch backing to minimize twisting of the coaxial cable.

10. A microwave stethoscope measurement apparatus according to claim 6 , wherein said microwave reception sensor is formed of a similar design as the transmission sensor.

11. A microwave stethoscope measurement method comprising the steps of:
providing a microwave transmission sensor and a microwave reception sensor mounted on a single chest patch in spaced-apart side-by-side configuration to be placed on a patient's chest to over a selected heart-lung location in the body of the patient, wherein the side-by-side microwave transmission and reception sensors are spaced apart a separation distance between sensors in lateral chest orientation selected in order to minimize attenuation of the returned microwave signal and/or electromagnetic coupling between the sensors so as to provide an optimal returned microwave signal for analysis of lung water content and other vital signs of the patient, transmitting a microwave radiating signal via the microwave transmission sensor on the chest patch through the skin and into tissues at the selected heart-lung location in the patient's body and receiving a returned microwave scattering signal via the microwave reception sensor on the chest patch, applying digital signal processing of the returned microwave scattering signal for extracting output data indicative of lung water content of the patient's medical condition, displaying the output data on a display for monitoring the patient's medical condition.

12. A microwave stethoscope measurement method according to claim 11 , wherein said applied digital signal processing also extracts output data indicative of the patient's vital signs, and other critical measurements.

13. A microwave stethoscope measurement method according to claim 11 , wherein said applied digital signal processing also extracts output data indicative of the patient's stroke volume and/or cardiac output.

14. A microwave stethoscope measurement method according to claim 11 , wherein the microwave transmission and reception sensors are placed on the patient's chest spaced apart a separation distance of about 1-3 cm between sensors in lateral chest orientation.

15. A microwave stethoscope measurement method according to claim 11 , wherein said microwave transmission sensor is fed a microwave signal having a frequency range from about 700 MHz to 1.5 GHz.

16. A microwave stethoscope measurement method according to claim 15 , wherein said frequency range is from about 915 MHz and 920 MHz allocated for medical and industrial applications (ISM band).

17. A microwave stethoscope measurement apparatus according to claim 11 , wherein said microwave transmission sensor is a broadband sensor for multi-frequency measurements.

18. A microwave stethoscope measurement method according to claim 11 , wherein said microwave transmission and reception sensors are fabricated with a textile fabric for wearer comfort and to improve contact with the patient's skin.

19. A microwave stethoscope measurement method according to claim 11 , wherein said applied digital signal processing step comprises:
employing a short time Fourier Transform (STFT) spectrum windowed-averaged algorithm for extraction of waveforms for respiration rate (RR) and lung water content (LWC),
comparing the lung water content (LWC) waveform from the returned microwave signal to the transmitted microwave signal in order to extract a change of phase and magnitude of phase change indicative of LWC measurement and change in LWC measurement, and
band-pass filtering the extracted waveforms to isolate a heartbeat waveform, then applying a threshold-based peak detection algorithm to select highest peaks in each heartbeat and ignores smaller ones, and calculating a heart rate (HR) by counting the number of peaks in a given interval.

20. A microwave stethoscope measurement method according to claim 11 , wherein said output data is transmitted wirelessly to a mobile digital communication device for remote monitoring of a patient's medical condition.

Assignees

• Iskander Magdy F
• Celik Nuri
• Gagarin Ruthsenne
• Huang Gui Chao
• Bibb Darcy Alan
• Univ Hawaii

Inventors

• Iskander Magdy F
• Celik Nuri
• Gagarin Ruthsenne
• Huang Gui Chao
• Bibb Darcy Alan

Classifications

• A61B5/0816

  Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00) · CPC title

• A61B5/0507 Primary

  using microwaves or terahertz waves · CPC title

• A61B5/0205

  Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition · CPC title

• A61B5/4878

  Evaluating oedema · CPC title

• A61B5/02444

  Details of sensor (A61B5/02427 takes precedence) · CPC title